Environmentally-friendly multi-layer flexible film having barrier properties

ABSTRACT

A multi-layer film with barrier properties having two or more layers made from a bio-based film is disclosed. In one aspect, the print web comprises a bio-based film. In one aspect, the barrier web comprises a bio-based film. In one aspect, a bio-based adhesive adheres the print web to the barrier web. The bio-based film can include paper, PCR, polylactide or polyhydroxy-alkanoate. Unlike prior art petroleum-based films, the bio-based film of the present invention is made from a renewable resource and is biodegradable.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 11/464,331, filed Aug. 14, 2006, and acontinuation-in-part of co-pending U.S. patent application Ser. No.11/848,775, filed Aug. 31, 2007, the technical disclosures of which arehereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a biodegradable, bio-based flexiblepackaging material that can be used in packaging food products and to amethod of making the bio-based packaging material.

2. Description of Related Art

Multi-layered film structures made from petroleum-based productsoriginating from fossil fuels are often used in flexible packages wherethere is a need for its advantageous barrier, sealant, andgraphics-capability properties. Barrier properties in one or more layersare important in order to protect the product inside the package fromlight, oxygen or moisture. Such a need exists, for example, for theprotection of foodstuffs, which may run the risk of flavor loss,staling, or spoilage if insufficient barrier properties are present toprevent transmission of such things as light, oxygen, or moisture intothe package. In addition, barrier properties also prevent undesirableleaching of the product to the outside of the bag. For example, oilyfoods such as potato chips have the potential for some oil to leach outinto the film of the bag. The sealant properties are important in orderto enable the flexible package to form an airtight or hermetic seal.Without a hermetic seal, any barrier properties provided by the film areineffective against oxygen, moisture, or aroma transmission between theproduct in the package and the outside. A graphics capability is neededbecause it enables a consumer to quickly identify the product that he orshe is seeking to purchase, allows food product manufacturers a way tolabel the nutritional content of the packaged food, and enables pricinginformation, such as bar codes to be placed on the product.

One prior art multi-layer or composite film used for packaging potatochips and like products is illustrated in FIG. 1 which is a schematic ofa cross section of the multi-layer film 100 illustrating each individualsubstantive layer. Each of these layers functions in some way to providethe needed barrier, sealant, and graphics capability properties. Forexample, the graphics layer 114 is typically used for the presentationof graphics that can be reverse-printed and viewed through a transparentouter base layer 112. Like numerals are used throughout this descriptionto describe similar or identical parts, unless otherwise indicated. Theouter base layer 112 is typically oriented polypropylene (“OPP”) orpolyethylene terephthalate (“PET”). A metal layer disposed upon an innerbase layer 118 provides the required barrier properties. It has beenfound and is well-known in the prior art that by metallizing apetroleum-based polyolefin such as OPP or PET reduces the moisture andoxygen transmission through the film by approximately three orders ofmagnitude. Petroleum-based OPP is typically utilized for the base layers112 118 because of its lower cost. A sealant layer 119 disposed upon theOPP layer 118 enables a hermetic seal to be formed at a temperaturelower than the melt temperature of the OPP. A lower melting pointsealant layer 119 is desirable because melting the metallized OPP toform a seal could have an adverse effect on the barrier properties.Typical prior art sealant layers 119 include an ethylene-propyleneco-polymer and an ethylene-propylene-butene-1 ter-polymer. A glue orlaminate layer 115, typically a polyethylene extrusion, is required toadhere the outer base layer 112 with the inner, product-side base layer118. Thus, at least two base layers of petroleum-based polypropylene aretypically required in a composite or multi-layered film.

Other materials used in packaging are typically petroleum-basedmaterials such as polyester, polyolefin extrusions, adhesive laminates,and other such materials, or a layered combination of the above.

FIG. 2 demonstrates schematically the formation of material, in whichthe OPP layers 112, 118 of the packaging material are separatelymanufactured, then formed into the final material 100 on an extrusionlaminator 200. The OPP layer 112 having graphics 114 previously appliedby a known graphics application method such as flexographic orrotogravure is fed from roll 212 while OPP layer 118 is fed from roll218. At the same time, resin for PE laminate layer 115 is fed intohopper 215 a and through extruder 215 b, where it will be heated toapproximately 600° F. and extruded at die 215 c as molten polyethylene115. This molten polyethylene 115 is extruded at a rate that iscongruent with the rate at which the petroleum-based OPP materials 112,118 are fed, becoming sandwiched between these two materials. Thelayered material 100 then runs between chill drum 220 and nip roller230, ensuring that it forms an even layer as it is cooled. The pressurebetween the laminator rollers is generally set in the range of 0.5 to 5pounds per linear inch across the width of the material. The large chilldrum 220 is made of stainless steel and is cooled to about 50-60° F., sothat while the material is cooled quickly, no condensation is allowed toform. The smaller nip roller 230 is generally formed of rubber oranother resilient material. Note that the layered material 100 remainsin contact with the chill drum 220 for a period of time after it haspassed through the rollers, to allow time for the resin to coolsufficiently. The material can then be wound into rolls (notspecifically shown) for transport to the location where it will be usedin packaging. Generally, it is economical to form the material as widesheets that are then slit using thin slitter knives into the desiredwidth as the material is rolled for shipping.

Once the material is formed and cut into desired widths, it can beloaded into a vertical form, fill, and seal machine to be used inpackaging the many products that are packaged using this method. FIG. 3shows an exemplary vertical form, fill, and seal machine that can beused to package snack foods, such as chips. This drawing is simplified,and does not show the cabinet and support structures that typicallysurround such a machine, but it demonstrates the working of the machinewell. Packaging, film 310 is taken from a roll 312 of film and passedthrough tensioners 314 that keep it taut. The film then passes over aformer 316, which directs the film as it forms a vertical tube around aproduct delivery cylinder 318. This product delivery cylinder 318normally has either a round or a somewhat oval cross-section. As thetube of packaging material is pulled downward by drive belts 320, theedges of the film are sealed along its length by a vertical sealer 322,forming a back seal 324. The machine then applies a pair, ofheat-sealing jaws 326 against the tube to form a transverse seal 328.This transverse seal 328 acts as the top seal on the bag 330 below thescaling jaws 326 and the bottom seal on the bag 332 being filled andformed above the jaws 326. After the transverse seal 328 has beenformed, a cut is made across the sealed area to separate the finishedbag 330 below the seal 328 from the partially completed bag 332 abovethe seal. The film tube is then pushed downward to draw out anotherpackage length. Before the sealing laws form each transverse seal, theproduct to be packaged is dropped through the product delivery cylinder318 and is held within the tube above the transverse seal 328.

Petroleum-based prior art flexible films comprise a relatively smallpart of the waste produced when compared to other types of packaging.Thus, it is uneconomical to recycle because of the energy required tocollect, separate, and clean the used flexible film packages. Further,because the petroleum films are environmentally stable, petroleum basedfilms have a relatively low rate of degradation. Consequently, discardedpackages that become inadvertently dislocated from intended wastestreams can appear as unsightly litter for a relatively long period oftime. Further, such films can survive for long periods of time in alandfill. Another disadvantage of petroleum-based films is that they aremade from oil, which many consider to be a limited, non-renewableresource. Further, the price of petroleum-based films is volatile sinceit is tied to the price of oil. Consequently, a need exists for abiodegradable flexible film made from a renewable resource. In oneembodiment, such film should be food safe and have the requisite barrierproperties to store a low moisture shelf-stable food for an extendedperiod of time without the product staling. The film should have therequisite sealable and coefficient of friction properties that enable itto be used on existing vertical form, fill, and seal machines.

SUMMARY OF THE INVENTION

The present invention is directed towards a multi-layer film havingbarrier properties wherein each of two or more layers comprises abio-based film. In one aspect, the multi-layer packaging film of thepresent invention has an outer layer comprising a bio-based film, anadhesive layer adhered to the outer layer and a product side layercomprising a bio-based film having barrier properties. In one aspect,the bio-based film is selected from a paper comprising post consumerrecycled fiber, polylactide (PLA), and polyhydroxy-alkanoate (PHA). Inone aspect, the adhesive layer comprises a bio-based film. The presentinvention thereby provides a multi-layer film with barrier propertiesthat is substantially made from renewable resources. Further, in oneembodiment, a substantial portion of the film is biodegradable. Theabove as well as additional features and advantages of the presentinvention will become apparent in the following written detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbe best understood by reference to the following detailed description ofillustrative embodiments when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 depicts a cross-section of an exemplary prior art packaging film;

FIG. 2 depicts the exemplary formation of a prior art packaging film;

FIG. 3 depicts a vertical form, fill, and seal machine that is known inthe prior art;

FIG. 4 a depicts a magnified schematic cross-section of a hybridmulti-layer packaging film made according to one embodiment of theinvention;

FIG. 4 b depicts a magnified schematic cross-section of a hybridmulti-layer packaging film made according to one embodiment of theinvention;

FIG. 5 a depicts a magnified schematic cross-section of a multi-layerpackaging film made according to one embodiment of the invention; and

FIG. 5 b depicts a magnified schematic cross-section of a multi-layerpackaging film made according to one embodiment of the invention

DETAILED DESCRIPTION

One embodiment of the present invention is directed towards use of abio-based film as at least two of the film layers in a multi-layerflexible film packaging. As used herein, the term “bio-based film” meansa polymer film where at least 80% of the polymer film by weight isderived from a non-petroleum or biorenewable feedstock. In oneembodiment up to about 20% of the bio-based film can comprise aconventional polymer sourced from petroleum

One problem with bio-based plastic films is that such films have poormoisture barrier and oxygen barrier properties. As a result, such filmsheretofore could not be used exclusively in packaging. Further, manybiodegradable films are brittle and stiffer than OPP typically used forflexible film packages. The handling of containers made exclusively frombiodegradable films is therefore relatively noisy as compared to priorart petroleum-based films. Many of these problems can minimized oreliminated by using a “hybrid” film.

One embodiment of the present invention is directed towards use of abio-based film comprising recycled material as at least one of the filmlayers in a multi-layer flexible film packaging. In one embodiment, thepresent invention is directed towards a flexible film comprising anouter paper layer comprising post consumer reclaim (“PCR”) fibers. Asused herein the term “PCR fibers” refers to fibers that are made fromrecycled paper. As used herein, the term “PCR paper” refers to papermade from a cellulose-based material that comprises PCR fibers.

FIG. 4 a depicts a magnified schematic cross-section of a multi-layerpackaging film 400 a made with recycled materials according to oneembodiment of the invention. The multi-layer film 400 a depicted in FIG.4 a is a hybrid film because it comprises both a biodegradable,bio-based film comprising recycled materials in the form of PCR paper402 a and a stable, metalized OPP film 418. Examples of metalized OPPfilms 418 having a sealant layer 419 that can be used in accordance withthe present invention include PWX-2, PWX-4, PWS-2 films available fromToray Plastics of North Kingstown, R.I. or MU-842, Met HB, or METALLYTEfilms available from Exxon-Mobil Chemical.

In the embodiment shown in FIG. 4 a, the outer base layer 402 acomprises PCR paper. In one embodiment, the outer base layer 402 acomprises food-safe PCR paper. As used herein, “food-safe PCR paper” isdefined as the absence of any harmful or deleterious materials (such as‘fluorescent whitening agents’) that can migrate to food products fromrecycled papers used for food packaging. U.S. Food and DrugAdministration regulation 21 CFR 176.260 prohibits the presence of anyharmful or deleterious materials that can migrate to food products fromrecycled papers used for food packaging. Food-safe PCR paper can be madefrom recycled paper-based feedstocks, as illustrated by U.S. applicationPublication No. 2005/0194110 and U.S. Pat. Nos. 6,294,047 and 6,387,211.Any reference in this specification to “PCR paper” is meant to alsoexplicitly encompass “food safe PCR paper.”

PCR paper fibers can be added to the virgin paper fibers during typicaland conventional paper making processes during the wet mixing stage. ThePCR fibers or PCR and virgin fibers are dried across a drum roll to formthe paper sheet. The PCR fibers thereby replace a portion of all of thevirgin fibers. In one embodiment, the outer base layer 402 a comprisesPCR paper which further comprises between about 5% and about 100% PCRfiber by weight of the outer base layer 402. Further, in one embodiment,the present invention comprises a multi-layer film 400 a comprising PCRpaper, wherein the multi-layer film 400 a comprises between about 1.25%and about 70% PCR fibers by total weight of the multi-layer film 400 a.

Unlike plastic sheets of film where the thickness of the film ismeasured in “gauge”, the thickness of paper is measured in pounds perream and refers to the weight of 432,000 square inches of film. In oneembodiment, the outer base layer 402 a comprises between about 15 poundsand about 30 pounds per ream. In one embodiment, the PCR paper comprisesbetween about 25% and about 70% and more preferably about 50% by weightthe laminate film 400 a.

A sheet of PCR paper can be processed like most thermoplastic polymersinto a multi-layer film. For example, in one embodiment, the PCR paperis sent to a converter for printing and lamination. Referring again toFIG. 4 a, a graphic image 414 a is printed on the outer-facing of theouter base layer 402 a. Printing can take place via any number ofconventional printing processes (flexographic, rotogravure, off-set,etc.). One problem with recycled paper films is that such films havepoor moisture barrier and oxygen barrier properties. As a result, suchfilms cannot currently be used exclusively in packaging low moistureshelf stable food products. Consequently, a laminate layer 415 can beused to “glue” the PCR paper sheet 402 a to a metalized OPP film 418 orother barrier property layer having a sealant layer 419 with eitherconventional extrusion lamination (using molten polyethylene or similarmaterial) or with adhesive lamination (either solvent or solvent-less).

In the embodiment shown in FIG. 4 a, the inside sealant layer 419 can befolded over and then sealed on itself to form a tube having a fin sealfor a backseal. The fin seal is accomplished by the application of heatand pressure to the film. Alternatively, a thermal stripe can beprovided on the requisite portion of the PCR sheet 402 a adjacent or ontop of the graphics layer 414 to permit a lap seal to be used.

Whereas the prior art outside film 112, laminate layer 115 and innerbase layer 118 (as shown in FIG. 1) roughly were each one-third of thepackage film by weight, in one embodiment, the multi-layer film 400 a ofthe present invention comprises an outside PCR paper 402 a (as shown inFIG. 4 a) of 50% by weight of the multi-layer film 400 a. Consequently,less OPP film can be used than is required in the prior art reducingconsumption of fossil fuel resources.

In one embodiment, the total thickness of polyolefin films used in thelaminate layer 415, and in the metalized OPP layer 418 and sealant layer419 is less than 2.0 mils and more preferably less than about 1.5 mils.For example, referring to FIG. 4 a, in one embodiment, the laminatelayer 415 comprises a thickness of about 70 gauge, and the metalized OPPlayer 418 and sealant layer combined comprises a thickness of about 70gauge, resulting in a total polyolefin thickness of about 1.4 mils.

In one embodiment, the present invention provides a film comprising PCRpaper wherein the film has between 25% and 70% less polyolefins thanprior art films yet comprises acceptable oxygen and moisture barrierproperties. As used herein, a film having acceptable oxygen barrierproperties has an oxygen transmission rate of less than about 150cc/m²/day (ASTM D-3985). As used herein, a film having acceptablemoisture barrier properties comprises a water vapor transmission rate ofless than about 5 grams/m²/day (ASTM F-1249). As used herein, a barrierproperty layer comprises a film having acceptable moisture and oxygenbarrier properties.

FIG. 4 b depicts a magnified schematic cross-section of a hybridmulti-layer packaging film 400 b made according to one embodiment of theinvention. Here, the outer transparent base layer comprises abiodegradable, bio-based film 402 b in place of an orientedpetroleum-based polypropylene 112 depicted in FIG. 1.

In one embodiment, the biodegradable, bio-based film 402 b comprisespolylactic acid, also known as polylactide (“PLA”), which is abiodegradable, thermoplastic, aliphatic polyester derived from lacticacid. PLA can be easily produced in a high molecular weight form throughring-opening polymerization of lactide/lactic acid to PLA by use of acatalyst and heat.

PLA can be made from plant-based feedstocks including soybeans, asillustrated by U.S. Patent Application Publication Number 20040229327 orfrom the fermentation of agricultural by-products such as corn starch orother plant-based feedstocks such as corn, wheat, or sugar beets. PLAcan be processed like most thermoplastic polymers into a film. PLA hasphysical properties similar to PET and has excellent clarity. PLA filmsare described in U.S. Pat. No. 6,207,792 and PLA resins are availablefrom Natureworks LLC (http://www.natuureworksllc.com) of Minnetonka,Minn. PLA degrades into carbon dioxide and water.

In one embodiment, the biodegradable, bio-based film 402 b comprisespolyhydroxy-alkanoate (“PHA”), available from Archer Daniels Midland ofDecatur, Ill. PHA is a polymer belonging to the polyesters class and canbe produced by microorganisms (e.g. Alcaligenes eutrophus) as a form ofenergy storage. In one embodiment, microbial biosynthesis of PHA startswith the condensation of two molecules of acetyl-CoA to giveacetoacetyl-CoA which is subsequently reduced to hydroxybutyryl-CoA.Hydroxybutyryl-CoA is then used as a monomer to polymerize PHB, the mostcommon type of PHA.

The laminate film depicted in FIG. 4 b can be made by extruding abiodegradable bio-based film 402 b into a film sheet. In one embodiment,the bio-based film 402 b has been oriented in the machine direction orthe transverse direction. In one embodiment, the bio-based film 402 bcomprises a biaxially oriented film. Such biaxially oriented film isavailable as a PLA film from SKC Ltd. of South Korea. In one embodiment,PLA film 402 b used comprises a thickness of between about 70 gauge andabout 120 gauge. Although PLA film is the bio-based film most oftenreferred to in this application, such film is provided only as anexample of a bio-based film and the disclosure should in no way beinterpreted as being limited to PLA. Consequently, the terms “PLA film”and “bio-based film” should be construed as interchangeable throughoutthe specification unless specific properties of PLA are being addressed.A graphic image 414 is reverse printed onto the biodegradable, bio-basedfilm 402 b by a known graphics application method such as flexographicor rotogravure to form a graphics layer 414. This graphics layer 414 canthen be “glued” to the product-side metalized OPP film 418, by alaminate layer 415, typically a polyethylene extrusion. Thus, the priorart OPP print web is replaced with a biodegradable print web. In oneembodiment, the bio-based film 402 b comprises multiple layers toenhance printing and coefficient of friction properties. In oneembodiment, the bio-based film 402 b comprises one or more layers ofPLA.

In the embodiment shown in FIG. 4 b, the inside sealant layer 419 can befolded over and then sealed on itself to form a tube having a fin sealfor a backseal. The fin seal is accomplished by the application of heatand pressure to the film. Alternatively, a thermal stripe can beprovided on the requisite portion of the bio-based film 402 b to permita lap seal to be used.

Examples of metalized OPP films 418 having a sealant layer 419 that canbe used in accordance with the present invention include PWX-2, PWX-4,PWS-2 films available from Toray Plastics of North Kingstown, R.I. orMU-842, Met HB, or METALLYTE films available from Exxon-Mobil Chemical.

The laminate of film depicted in FIG. 4 b is a hybrid film because itcomprises both a biodegradable, bio-based film 402 b and a stable,metalized OPP film 418. However, one benefit of the present invention isthat the outer PLA film 402 b can be made thicker than prior art outerfilms to maximize the use of bio-based films 402 b and thebiodegradability of the overall package while preserving “bag feel”properties that consumers have become so well known to consumers. Forexample, whereas the prior art outside film 112, laminate layer 115 andinner base layer 118 roughly were each one-third of the package film byweight, in one embodiment, the laminate of the present inventioncomprises an outside bio-based film 402 b of 50% by weight, a laminatelayer 415 being 20% by weight and an inner base OPP layer 418 of about30% by weight of the total packaging film. Consequently, less OPP film418 can be used than is required in the prior art reducing consumptionof fossil fuel resources. In one embodiment, the present inventionprovides a hybrid film having at least about one-quarter less andpreferably between about one-third and one-half less fossil fuel-basedcarbon than a prior art film, yet comprises acceptable barrierproperties.

There are several advantages provided by the hybrid film depicted inFIG. 4 b. First, biodegradable films 402 b such as PLA make excellentprint webs. Unlike polypropylene, PLA has oxygen in the backbone of themolecule. The oxygen inherently provides high surface energy thatfacilitates ink adhesion, thereby reducing the amount of pre-treatmentrequired to prepare the film for print as compared to prior artpetroleum-based OPP films. Second, the film can be produced using thesame existing capital assets that are used to make prior art films.Third, the hybrid film uses 25% to 50% less petroleum than prior artfilms. Fourth, the film is partially degradable which can help to reduceunsightly litter.

FIG. 5 a depicts a magnified schematic cross-section of a multi-layerpackaging film made according to one embodiment of the invention. Here,the inner base layer comprises a thin metalized barrier/adhesionimproving film layer 516 a adjacent to a biodegradable, bio-based film518 a such as PLA instead of an oriented polypropylene 118 418 depictedin FIG. 1 and FIG. 4 a, and FIG. 4 b.

A tie layer (not shown) can be disposed between the metalizedbarrier/adhesion improving film layer 516 a and the bio-based film layer518 a. A tie layer can permit potentially incompatible layers to bebonded together. The tie layer can be selected from malic anhydride,ethylenemethacrylate (“EMA”), and ethylenevinylacetate (“EVA”).

The metalized barrier/adhesion improving film layer 516 a adjacent tothe bio-based film 518 a can be one or more polymers selected frompolypropylene, an ethylene vinyl alcohol (“EVOH”) formula, polyvinylalcohol (“PVOH”), polyethylene, polyethylene terephthalate, nylon, and anano-composite coating. The metalized barrier/adhesion improving layer516 a can be adhered to the bio-based print web 502 with any suitableadhesive 515 a such as LDPE.

Below depicts EVOH formulas in accordance with various embodiments ofthe present invention.

The EVOH formula used in accordance with the present invention can rangefrom a low hydrolysis EVOH to a high hydrolysis EVOH. As used herein alow hydrolysis EVOH corresponds to the above formula wherein n=25. Asused herein, a high hydrolysis EVOH corresponds to the above formulawherein n=80. High hydrolysis EVOH provides oxygen barrier propertiesbut is more difficult to process. When metalized, EVOH providesacceptable moisture barrier properties. The EVOH formula can becoextruded with the PLA 518 and the EVOH formula can then be metalizedby methods known in the art including vacuum deposition.

In one embodiment, the metalized film 516 comprises a metalized PET 516that is less than about 10 gauge and preferably between about 2 andabout 4 gauge in thickness. The PET can be coextruded with the PLA 518and the PET can then be metalized by methods known in the art. In oneembodiment, the metalized film 516 comprises a PVOH coating that isapplied to the PLA as a liquid and then dried.

In one embodiment, one or both bio-based films 502 518 consists of onlyPLA. Alternatively, additives can be added to the print web bio-basedfilm 502 or the barrier web bio-based film 518 during the film makingprocess to improve film properties such as the rate of biodegradation.For example, the rate of degradation of biodegradable PLA is relativelyslow. Consequently, pieces of litter are still visible for a period oftime. To accelerate breakdown of PLA, starch can be added to the basepolymer to improve the biodegradability of the final film. In oneembodiment, one or both bio-based films 502 518 comprises about 1% toabout 65% starch by weight of the film. The starch will cause theoriented PLA film to breakdown into smaller pieces (roughly akin to onechewing food). These smaller pieces will then be far less visible in theenvironment as litter and will as degrade faster due to the largersurface area because the larger edge area allows moisture to seep inbetween the multi-layer film layers and breaks down the layers faster.Although starch addition discussed above is in relation to the two baselayers 502 518, starch can be incorporated into any bio-based layer,including any bio-based adhesive layer discussed below. Starch can alsobe incorporated in any extruded tie/adhesive layer.

In one embodiment, the starch used comprises starch reclaimed from aprocessed food product. For example, when potatoes are sliced to makepotato chips, tile sliced potatoes are often washed to remove surfacestarch prior to frying the potato slices to prevent the potato slicesfrom sticking together. The starch that is washed off from the potatoslices can be reclaimed and incorporated into any PLA-based layer.Consequently, such embodiment advantageously both reduces waste disposalcosts and at the same time reduces the amount of PLA needed for thepackaging film because a portion of the film can be made from reclaimedpotato starch. Because the starch and the PLA are both biologicalpolymers, they are compatible. Of course, such example of reclaimedstarch is provided for purposes of illustration and not limitation.

A PLA based film ultimately breaks down into CO₂ and H₂O. Degradation ofbio-based films can also be enhanced by adding various Transition metalstereates (Cobalt, Nickel, etc) but use of a starch would be preferredas it would also break down and leave no residual. In one embodiment,one or both bio-based films 502 518 comprises up to about 5% of astearate additive by weight of the film. One or more stearate additivescan be selected from aluminum, antimony, barium, bismuth, cadmium,cerium, chromium, cobalt, copper, gallium, iron, lanthanum, lead,lithium, magnesium, mercury, molybdenum, nickel, potassium, rare earths,silver, sodium, strontium, tin, tungsten, vanadium, yttrium, zinc orzirconium. Such additives are marketed under the TDPA tradename and areavailable from EPI of Conroe, Tex., USA. In one embodiment, one or bothbio-based films 502 518 comprises a photocatalyst. Photocatalysts areknown in the art and are typically used in 6-pack beverage can containerrings to facilitate breakdown upon exposure to sunlight.

Further, one or more suitable co-polymer additives can be used selectedfrom ethylene methlacrylate and styrene-butydiene block co-polymer(e.g., tradename KRATON) as a compatilizer to improve the degree ofcompatibility between the bio-based film 502 518 and other film layers.For example, such co-polymer additives can be used to improve the heatseal characteristics of the laminate film. The co-polymer additives canalso improve the lamination bond strength to help the biodegradable filmprint web to better adhere to an OPP barrier web, or to help thebio-based film print web to better adhere to a bio-based barrier web.Additives can also be used such that a biodegradable adhesive, e.g., thelaminate layer, can be used. An optional sealant layer 519 can also beprovided.

Whereas the prior art outside film 112, laminate layer 115 and innerbase layer 118 (as shown in FIG. 1) roughly were each one-third of thepackage film by weight, in one embodiment, the multi-layer film 500 a ofthe present invention comprises two bio-based layers 502 518 (as shownin FIG. 5 a) that together constitute between about 35% to about 75% byweight of the multi-layer film 500 a. Consequently, one embodiment ofthe present invention provides a bio-based multi-layer film comprisingtwo bio-based film layers wherein the multi-layer film has over 60% lessfossil fuel-based polyolefins than prior art films, provides abiodegradable film, yet comprises acceptable oxygen and moisture barrierproperties.

In one embodiment of the multi-layer film 500 a depicted in FIG. 5 a,the total thickness of polyolefin films used in the laminate layer 515 ais about 70 gauge or less, resulting in a total polyolefin thickness ofless than about 0.7 mils.

FIG. 5 b depicts a magnified schematic cross-section of a multi-layerpackaging film made according to one embodiment of the invention. Here,the multi-layer film comprises a bio-based adhesive 515 b. As usedherein, the term “bio-based adhesive” means a polymer adhesive where atleast about 80% of the polymer layer by weight is derived from anon-petroleum or biorenewable feedstock. The adhesive layer 515 b cancomprise any suitable biodegradable adhesive such as a modified PLAbiopolymer 26806 available from DaniMer Scientific LLC of Bainbridge, Gaor Mater Bi available from Novamont of Novara, Italy. In one embodiment,a starch based glue can be used.

Additives can also help to metalize a biodegradable film viaconventional aluminum vapor deposition processes to make a biodegradablebarrier web that provides barrier performance for the biodegradablefilm. Biodegradable films and bio-based films, such as PLA, arenotorious for having, poor barrier properties. As used herein, the term“additives” is not limited to chemical additives and can include surfacetreatment including, but not limited to, corona treatment.

In one embodiment, the bio-based film 518 b comprises a nanocoating 517to provide barrier protection. As used herein, a nanocoating comprises ananoclay, a nanocomposite or nanocomposite coating and any necessarybinder. Nanocomposites are known in the art as exemplified by U.S. Pat.No. 7,223,359, which is hereby incorporated by reference. In oneembodiment, the bio-based film comprises a nanoclay to provide barrierproperties. Nanoclays in accordance with the present invention compriselayered silicate platelets such as vermiculite, aluminosilicates,zeolites, bentonite, montmorillonite, kaolinite, bauxite, nontronite,beidellite, volkonskoite, hectorite, sponite, laponite, sauconite,hydrous mica, chlorite, magadiite, kenyaite, ledikite and mixturesthereof. Multiple polymer matrices known in the art can be used as abinder to “glue” the nanoclay or nanocomposite constituents togetherincluding, but not limited to an acrylic emulsion, styrene-acrylics, andpolyurethanes.

Nanocoatings advantageously provide nanoparticles in a structure on amicroscopic level having a flat, thin very large aspect ratio thatinhibits other molecules such as oxygen and water vapor from penetratingthe structure.

In one embodiment, a nanocoating or nanoclay can be added in the sametype of graphics application method presently used to apply an ink layerto a web of film. U.S. Pat. No. 6,232,389, which is hereby incorporatedby reference in its entirety, for example, discloses a coatingcomposition which contains substantially dispersed exfoliated layeredsilicates in an elastomeric polymer that can be applied as a coating anddried. In one embodiment, the coating is applied at a rate of less thanabout 15 grams of coating per square meter of area, more preferably lessthan about 10 grams/m² and even more preferably less than about 8grams/m². The free oxygen of PLA means that it has a natural affinityfor application of such coatings. In one embodiment, the nanoclay isadded to the bio-based film as an additive during film production.

In one embodiment, the layered silicate platelets of the nanocompositecomprise an aluminium-silicate that forms a substantially cylindrical orspherical structure. Hundreds of these structures can be coupledtogether can form long, thin tubes that are very difficult for oxygen orwater molecules to penetrate. In one embodiment, the nanocompositecomprises a pore size sufficient such that the navigation of an oxygenand/or water molecule through the nanocomposite pore is sufficientlyretarded to preserve the shelf-life of a low moisture food ingredient,such as a potato chip for two or more months in a biodegradable laminatebag comprising a nanocomposite for barrier properties. In oneembodiment, the platelets are bound so tightly together that there arevirtually no tube openings for the oxygen or water molecules to enter.In one embodiment, the nanocomposite comprises a scavenger that reactswith oxygen or water. In one embodiment, the nanocomposite comprises ascavenger such as iron.

In one embodiment, the barrier layer comprises a metalized nanocoating.For example, a nanocoating 517 such as a nanoclay or a nanocomposite canbe applied to any suitable film layer 518 b by any suitable method.Aluminum or other suitable material can then be applied by vapordeposition methods known in the art to provide a metalized layer 516 bover the nanocoating 517. Because PLA is a hygroscopic thermoplastic,the PLA film easily swells upon contact with moisture. Consequently, ametalized coating placed directly onto a PLA film has a very highpotential to crack after metallization when the adjacent PLA layer isexposed to moisture. Because a naked 80 gauge PLA film has a water vaportransmission rate of about 170 g/m²/day, it fails to provide therequisite moisture vapor transmission rate of less than 5 g/m²/day.Consequently, a cracked metalized coating will similarly fail to providea film with the requisite barrier properties. However, if a nanocoating517 is applied to a PLA layer 518 b and the nanocoating is metalized, itis believed that any subsequent cracks in the metal will havesubstantially less impact on the barrier properties of the film becauseof the barrier properties provided by the underlying nanocoating.

The water vapor transmission rates of various bio-based films wererecorded under various conditions and are depicted in Table 1 below. Therelatively humidity of the testing conditions, temperature at which thetest was conducted and the flow rate in standard cubic centimeters perminute are recorded in the table below. All PLA print web and backingweb films are 80 gauge films. The term “adhesive” signifies aconventional adhesive such as ROBOND was used. A modified PLA adhesivesignifies a modified PLA biopolymer 26806 from DaniMer was used. Thebond strength between the print web and backing web, if measured orobserved, is also provided below. An observation recorded as “Good”indicates that the layers could not be peeled apart by hand and therewere no obvious air pockets or other defects. A recording with “-”indicates that no measurement or observation was recorded. A numericalnumber is the actual recorded bond strength in grams per inch.

Samples 1-2 demonstrate the water vapor transmission rate of an aluminumoxide coated PLA layer adhered with an adhesive layer to a PLA printweb.

Samples 3-4 demonstrate the water vapor transmission rate of an aluminumoxide coating to two PLA layers.

Samples 5-12 demonstrate the water vapor transmission rate of variousmetalized blown PLA layers.

Samples 13-24 demonstrate the water vapor transmission rate of variousbiaxially oriented metalized PLA layers.

Samples 25-29 demonstrate the water vapor transmission rate of ananocomposite coated PLA. The Nanocompsite coating used was NANOLOK 3575from InMat Inc. Sample 29 had a coating weight of 3.6 g/m². The coatingweights of the other samples were not recorded.

Samples 30-40 demonstrate the water vapor transmission rate of “naked”PLA layers without the application of any barrier protection material. Atotal of 160 gauge of PLA is tested in samples 32-38 and a single 80gauge layer is tested in samples 39-40.

TABLE 1 Water Vapor Transmission Rate Measurements Sample WVTR PrintAdhesive RH T Q Bond No. g/m²/day Web Layer Backing Web (%) (° C.)(SCCM) (g/in) 1 31.25 PLA Adhesive AlO(x) PLA 72.80 37.5 29.70 Good 232.06 PLA Adhesive AlO(x) PLA 75.06 37.5 36.58 Good 3 10.34 AlO(x)Adhesive AlO(x) PLA 84.25 37.5 32.25 Good PLA 4 10.66 AlO(x) AdhesiveAlO(x) PLA 87.13 37.5 31.97 Good PLA 5 9.11 None None Metallized PLA79.21 37.5 10.50 n/a (Blown) 6 10.64 None None Metallized PLA 82.54 37.510.69 n/a (Blown) 7 5.14 PLA Adhesive Metallized PLA 81.03 37.5 10.60Good (Blown) 8 5.95 PLA Adhesive Metallized PLA 83.93 37.5 10.44 Good(Blown) 9 6.12 PLA Adhesive Metallized PLA 83.07 37.5 9.94 Good (Blown)10 5.29 PLA Adhesive Metallized PLA 86.95 37.5 10.55 Good (Blown) 1116.87 PLA Modified Metallized PLA 90.00 37.5 10.00 Easily PLA (Blown)peeled by hand 12 15.26 PLA Modified Metallized PLA 90.00 37.5 10.00Easily PLA (Blown) peeled by hand 13 1.13 None None Metallized PLA 80.5437.5 10.18 n/a 14 0.96 None None Metallized PLA 80.03 37.5 10.25 n/a 150.49 PLA Adhesive Metallized PLA 76.72 37.5 10.22 Good 16 0.51 PLAAdhesive Metallized PLA 78.65 37.5 10.26 Good 17 0.79 PLA AdhesiveMetallized PLA 79.70 37.5 10.45 Good 18 0.79 PLA Adhesive Metallized PLA82.68 37.5 13.14 Good 19 1.12 PLA Adhesive Metallized PLA 83.65 37.510.44 Good 20 1.38 PLA Adhesive Metallized PLA 87.22 37.5 10.37 Good 210.52 None None Metallized PLA 66.61 30.3 10.84 n/a 22 0.42 None NoneMetallized PLA 67.04 30.3 10.39 n/a 23 1.91 None None Metallized PLA85.53 35 10.84 n/a 24 2.18 None None Metallized PLA 85.85 35 10.49 n/a25 2.27 None None Nanocomposite 50.00 37.5 10.00 240.3 coated PLA 262.23 None None Nanocomposite 50.00 37.5 10.00 288.1 coated PLA 27 2.09None None Nanocomposite 50.00 37.5 10.00 293.6 coated PLA 28 2.11 NoneNone Nanocomposite 50.00 37.5 10.00 311.3 coated PLA 29 2.34 None NoneNanocomposite 55.2000 37.5 50.70 n/a coated PLA 30 113.54 PLA ModifiedPLA 72.2527 37.8 86.53 Good PLA 31 119.82 PLA Modified PLA 76.6374 37.891.27 Good PLA 32 131.85 PLA Adhesive PLA 71.1345 37.8 98.09 — 33 128.80PLA Adhesive PLA 70.1553 37.8 99.77 — 34 133.97 PLA Adhesive PLA 75.341237.8 101.08 — 35 117.89 PLA Adhesive PLA 69.9762 37.8 89.42 — 36 123.65PLA Adhesive PLA 73.8467 37.8 103.41 — 37 120.87 PLA Adhesive PLA70.6552 37.8 89.95 — 38 128.94 PLA Adhesive PLA 73.3303 37.8 99.40 — 39167.40 none none PLA 67.5000 30.3 100.00 — 40 167.60 none none PLA67.5000 30.3 100.00 —

The above table is useful for showing the relative barrier effectivenessof various bio-based multi-layer film combinations. For example, ananocoated PLA sheet has a WVTR of approximately 2 g/m²/day (at 55% RHand 37.5° C.), as shown by samples 25-29 above. By comparison, two testsof an uncoated 80 gauge PLA TE70C sheet from SKC of South Korea revealeda WVTR of approximately 170 g/m²/day (at 67.5% RH and 30° C.), as shownby samples 39-40 above.

Assuming a metalized nanocoated PLA sheet has a WVTR of 0.2 g/m²/day,and given that the metalized PLA sheet has a WVTR of about 1.0 g/m²/day(see samples 21-24 above), and given that a naked PLA sheet has a WVTRof about 170 g/m²/day, it becomes apparent that even if a portion of ametalized nanocoated PLA sheet has cracks in the metal coating, the WVTRthrough the nanocoated cracked areas is substantially less through thenanocoated sheet (at 2 g/m²/day) than through the naked PLA, sheet (at170 g/m²/day).

Using the above data, a simplified hypothetical example can be positedthat to demonstate the belief of the synergistic effectiveness of oneembodiment of the claimed invention. Its believed that a metalizednanocoating will provide surprisingly synergistic results than eithercoating alone because it is believed that the metalized nanocoated PLAsheet will have less cracking than a metalized PLA sheet (e.g., with nonanocoating) because of the physical properties of the nanocoating. Itsbelieved that a nanocoating of layered silicate platelets, for example,will not crack and are able to absorb some or all of the expansion ofthe underlying hydroscopic PLA layer (due to humidity, etc.) therebyreducing the amount of expansion exerted on the metalized layer andthereby reducing or eliminating cracking of the metalized layer. In oneembodiment, the nanocoating comprises an oxygen or moisture scavenger,such as iron powder and such scavenger can serve to inhibit moistureabsorption and subsequent expansion of the PLA film.

In one embodiment, more than one nanocoating is applied to themultilayer film to obtain an additive barrier effect. For example,referring to FIG. 5 b, in one embodiment a second nanocoating (notshown) can be applied between the ink layer 514 and the modified PLAlayer 515 b. In one embodiment, a nanocoating can be applied on theouter side of the bio-based film 502 as an overlacquer. In oneembodiment, a nanocoating is applied between the metal layer 516 b andthe adhesive layer 515 b. In one embodiment, a nanocoating is appliedoil the product side of the bio-based layer 518 b.

In embodiment depicted in FIG. 5 b, the present invention provides abio-based multi-layer film comprising three bio-based film layerswherein the multi-layer film has over 80% less polyolefins than theprior art film depicted in FIG. 1 yet comprises acceptable oxygen andmoisture barrier properties.

The present invention provides numerous advantages over traditional,petroleum-based prior art films. First, the present invention reducesconsumption of fossil fuels where the bio-based layer is being used forone or more layers of the film that previously required apetroleum-based/fossil-fuel based polypropylene polymer. In theembodiment where PCR is used as a film layer, the film of the presentinvention is made with both a renewable and a recycled resource.

Second, the present invention lowers the amount of carbon dioxide in theatmosphere because the origin of the bio-based films is plant-based.Although the bio-based film can degrade in a relatively short period oftime under composting conditions, if the film is placed into a landfillthe carbon dioxide is effectively sequestered away and stored because ofthe lack of light, oxygen, and moisture available to degrade to thefilm. Thus, the carbon dioxide that was pulled from the atmosphere bythe plant from which the bio-based film was derived is effectivelyplaced into storage. Further, in one embodiment, if the PCR papercomprises more than 80% of PCR fiber by weight, more carbon dioxide issequestered from the atmosphere than is used to make the PCR paper.Consequently, the present invention can be used to provide a carbondioxide sink for greenhouses gases.

Third, less litter is visible because a portion of the film making upthe resultant package is biodegradable. As used herein, the term“biodegradable” means that less than about 5% by weight and preferablyless than about 1% of the film remains after being left at 35° C. at 75%humidity in the open air for 60 days. Those skilled in the art willunderstand that at different ambient conditions, it may take longer forthe film to degrade. By comparison, an OPP film can last more than 100years under these same conditions. Unlike petroleum-based films,bio-based films easily degrade. PCR paper, for example, is made up ofcellulose molecules, which can be degraded through hydrolyticdegradation (upon exposure to water), oxidative degradation (uponexposure to oxygen), and thermal degradation (upon exposure to heat).All of these sources of degradation are available in the openenvironment. Consequently, one benefit of the present invention is thatthe amount of unsightly litter degrades more quickly.

Fourth, the film of the present invention can be produced using the sameexisting capital assets with only minor modifications that are used tomake prior art films.

Fifth, energy is conserved because it takes less energy to create a filmin accordance with the present invention than prior art petroleum basedflexible films. For example 1 kg of PLA requires only 56 megajoules ofenergy, which is 20% to 50% fewer fossil resources than required to makepetroleum-based plastics such as polypropylene.

Sixth, the invention provides more stable and less volatile pricing.Unlike petroleum-based commodities which fluctuate widely based upon theprice of oil, bio-based commodities are more stable and less volatile.Further, bio-based films have the potential to benefit from continualimprovements in genetically-engineered plants that can increase thedesired feedstock composition and yield.

As used herein, the term “package” should be understood to include anycontainer including, but not limited to, any food container made up ofmulti-layer thin films. The sealant layers, adhesive layers, print webs,and barrier webs as discussed herein are particularly suitable forforming packages for snack foods such as potato chips, corn chips,tortilla chips and the like. However, while the layers and filmsdiscussed herein are contemplated for use in processes for the packagingof snack foods, such as the filling and sealing of bags of snack foods,the layers and films can also be put to use in processes for thepackaging of other low moisture products. While this invention has beenparticularly shown and described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes in form and detail may be made therein without departingfrom the spirit and scope of the invention.

1. A multi-layer packaging film comprising: a) an outer layer comprisinga first bio-based film; b) an adhesive layer adjacent to said outerlayer; and c) a product side layer comprising a second bio-based filmhaving a nanocoating between said product side layer and said adhesivelayer to provide barrier properties, wherein said multi-layer packagingfilm comprises a moisture vapor transmission rate of less than about 5g/m2/day.
 2. The film of claim 1 wherein said adhesive layer comprises athird bio-based film.
 3. The film of claim 2 wherein said first, saidsecond or said third bio-based film comprises polylactide.
 4. The filmof claim 2 wherein said first, said second or said third bio-based filmcomprises polyhydroxy-alkanoate.
 5. The film of claim 2 wherein saidfirst bio-based film, said second bio-based film, and said thirdbio-based film comprise a total weight of bio-based film which is atleast 90% of said multi-layer packaging film by weight.
 6. The film ofclaim 2 wherein said first, said second or said third bio-based filmcomprises between about 1% and about 65% starch by weight of the film.7. The film of claim 2 wherein said first, said second or said thirdbio-based film further comprises a stearate additive.
 8. The film ofclaim 1 further comprising a metalized layer between said nanocoatingand said adhesive layer.
 9. A snack food package made from a multi-layerflexible film having barrier properties, said multi-layer flexible filmcomprises: an outer layer comprising a first bio-based film layer; anadhesive layer adjacent to said outer layer; and a product side layercomprising a second bio-based film layer having a nanocoating betweensaid product side layer and said adhesive layer to provide barrierproperties, wherein said multi-layer packaging film comprises a moisturevapor transmission rate of less than about 5 g/m2/day.
 10. The snackfood package of claim 9 wherein said first bio-based film layercomprises an ink layer .
 11. The snack food package of claim 9 whereinsaid first bio-based film layer comprises a barrier layer.
 12. The snackfood package of claim 9 wherein said second bio-based film layer furthercomprises PCR paper.
 13. The snack food package of claim 9 furthercomprising a metalized layer between said nanocoating and said adhesivelayer.